Currently, in a Long Term Evolution (LTE) system, uplink data and downlink data are scheduled by using a physical downlink control channel (PDCCH) or an enhanced physical downlink control channel (E-PDCCH) in a one-to-one scheduling manner. With development of communications technologies, an increase in a quantity of user connections and an increase in a quantity of potential concurrent access users pose a challenge to a control channel capacity. How control channel overheads are optimized becomes an important research direction.
An uplink contention transmission solution in which group-based scheduling is performed can effectively reduce scheduling signaling overheads. In the solution, by using a contention-based grant (CB-Grant), a base station schedules a plurality of user equipments (UE) that use a same contention resource, to perform uplink data transmission. To be specific, when scheduling a user group that uses the same contention resource to transmit uplink data, the base station may demodulate a demodulation reference signal (DMRS) sequence in each uplink data to distinguish between data sent by the UEs, so as to reduce scheduling signaling overheads.
During a process of implementing the present disclosure, the inventor finds that the prior art has at least the following problems:
In a user group that contends for a same contention resource, there is a possibility of a transmission conflict due to a problem such as a poor inter-user matching degree for a virtual multiple-input multiple-output (MIMO) technology or poor inter-user DMRS sequence orthogonality. As a result, abase station cannot distinguish between data sent by UEs, and uplink data transmission fails. In this contention-based transmission mechanism, UE that fails in transmitting uplink data needs to retransmit the data on an original resource. In this case, a conflict still occurs in uplink data retransmission, and consequently the uplink data retransmission fails.